Wireless communication technologies are widely used in nowadays. FIG. 1A illustrates the schematic view of a conventional wireless communication system 1. The wireless communication system 1 comprises a user equipment 11, a relay station 13, a base station 15, and a core network 17. The user equipment 11 is wirelessly connected to the relay station 13, the relay station 13 is wirelessly connected to the base station 15, and the base station 15 is wiredly connected to the core network 17.
The relay station 13 extends the serving coverage of the core network 17 so that a user equipment that is not in the coverage of the base station 15 but in the coverage of the relay station 13, such as the user equipment 11, can access the services provided by the core network 17. The base station 15 communicates with the core network 17 via an S1 interface, while the user equipment 11 communicates with the core network 17 via a Non-Access Stratum (NAS) mechanism.
FIG. 1B illustrates the states and the state transitions of a conventional NAS mechanism that is used in the user equipment 11. In FIG. 1B, the ellipses indicate the states in the NAS mechanism, while the texts along the arrows indicate the operations. The user equipment 11 starts at an EPS Mobility Management (EMM)-Null state 101. After the user equipment 11 enables the S1 mode, it enters the EMM-Deregistered state 102. Next, the user equipment 11 will enter the EMM-RegisteredInitiated state 103 if it requests for an attachment to the core network 17. If the attachment request is accepted and the default bearer is activated, the user equipment 11 enters the EMM-Registered state 104. For some occasions, the user equipment 11 will initiate a service request to recall the bearer. One example of the occasions is when the user equipment 11 tries to wake up from the sleep mode. During the establishment of the bearer, the user equipment 11 is in the EMM-ServiceRequestInitiated state 105. After the bearer has been established, the user equipment 11 returns to the EMM-Registered state 104 again. Afterwards, the user equipment 11 enters the EMM-Deregistered state 102 again if it is detached from the core network 17.
In order to make the relay station 13 act like a base station to the user equipment 11, the relay station 13 has to create a backhaul connection (i.e. the S1 interface) to communicate with the core network 17 so that it can translate the backhaul control messages received from the user equipment 11 and relay the translated backhaul control message to the core network 17. Additionally, the relay station 13 has to create a radio connection between itself and the core network 17.
No solution currently exists for a node in a wireless communication system to establish both a backhaul connection and a radio connection. Specifically, current technologies only support a base station to create a backhaul connection and support a user equipment to create a radio connection. According to the aforementioned descriptions, a mechanism and method for a node to create both a backhaul connection and a radio connection is needed.